The technology disclosed in Japanese Patent Application Laid-Open No. H5-13049/1993, as published, may be cited as first prior art for miniaturizing projection type liquid crystal display devices which magnify, project, and display images of liquid crystal display elements.
Disclosed in this publication is the configuration of a display device wherein three liquid crystal display elements are deployed about the periphery of a dichroic prism, the liquid crystal display elements are illuminated by flat-panel fluorescent tubes emitting different colors of light, respectively, deployed on the back sides of the liquid crystal display elements, and images of the several colors synthesized by the dichroic prism are projected on a screen by a projection lens.
As second prior art for miniaturizing projection type liquid crystal display devices, a configuration may be cited wherein only one liquid crystal display element is used, that liquid crystal display element is illuminated from the back side thereof by a lamp such as a metal halide lamp, and the image of the liquid crystal display element is projected onto a screen by a projection lens.
With the first prior art, cited above, however, because three liquid crystal display elements are used, costs becomes high, which is a problem, and an adjustment mechanism become necessary for keeping the images of the three liquid crystal display elements from shifting out of place, which makes it very difficult to realize further miniaturization in the display devices, which is also a problem.
With the second prior art, cited above, moreover, the light source is a white light source, making it necessary to have color filters in the pixels of the liquid crystal display element in order to project color images. Three pixels, namely a red, a green, and a blue pixel are necessary in order to generate colors, whereupon display image resolution deteriorates, and, since light other than that of the transmission wavelength is absorbed by the color filters, the display images become dark, which is a problem. In addition, a high voltage is required for lighting the metal halide lamp, which means that the power supply circuit becomes large, thus making it very difficult to miniaturize the display device, which is a problem.